Determining which interventions work best is important to service users, practitioners and policy makers.
Individual research studies are rarely sufficient to justify the use of new interventions. To make fair judgements, decisions should be informed by all relevant research evidence, including studies with findings in favour of and against the intervention under consideration. This is not straightforward. Studies with negative findings can remain unpublished. Studies may be flawed or reported over optimistically and are likely to be time and context dependent. Many are too small to reach reliable conclusions, and individual studies often appear to have conflicting findings.
Systematic reviews use objective and transparent methods to identify, evaluate and summarise all relevant research findings. To avoid bias, the approach and methods, are set out in advance. When carried out well, systematic reviews provide the most reliable evidence about the effects of tests, treatments and other interventions used in health and social care.